Spacing device fob renewable fuses



Aug. 7, 195] F. G. VON HOORN SPACING DEVICE FOR RENEWABLE FUSE FiledMarch 3, 1949 Fig. 2.

Fig.1.

InQeh c/or P1? or y gy H! s Attovn y.

Patented Aug. 7, 1951 UNITED SPACING DEVICE FOR RENEWABLE FUSES Fred G.von Hoorn, Nichols, Conn, assignor to General Electric Company, acorporation of New York Application March 3, 1949, Serial No. 79,404

My invention relates to electric fuses and more particularly toimprovements in spacing devices for electric fuses of the renewable fuselink type.

Current flowing in the fusible link member of an electric fuse of thetype mentioned causes heating of the link and accompanying expansionthereof. Since the ends of the link are fixed relative to the centerportion, buckling of the link tends to occur and physical contactfrequently results between the heated link and the fiber bar supportingthe fuse terminals and the link. Heat from the link is transmitted intothe fiber support, causing heating and charring of the portions of fibernearest the link. Uneven drying of the fiber bar tends to cause warpingthereof which in turn causes the terminals to be dis-. torted from theirnormal positions, resulting in loss of mechanical strength and poorexternal contact. Furthermore, abnormal conduction of heat away from thelink member disturbs the predetermined thermal characteristics thereof,resulting in defective calibration of the fuse. This is particularly thecase when links are used in multiple to increase the normal rating ofthe fuse, since buckling of the links frequently permits adjacent linksto come in contact with each other, thereby greatly disturbing thethermal characteristics of the combination of links.

Accordingly, it is an object of my invention to provide a new andimproved spacing device integral with each of the link members of anelectric fuse of the renewable type, to restrict buckling action of thelink members due to heating by a current flowing therein.

It is a further object of my invention to provide a new and improvedspacing device attachable to the supporting bar of a fuse of the typementioned, to restrict warping action of the support-. ing bar,resulting from the transmission of heat thereto from the heated linkmember of the fuse.

With these and other objects in view, attention is now directed to thefollowing description taken in connection with the figures of theaccompanying drawing in which the features of my invention believed tobe novel are set forth.

Fig. 1 represents a longitudinal sectional side view of an electric fuseof the renewable knife blade contact type, in which an embodiment of myinvention comprising a duality of spacing devices shown.

Fig, 2 is a front view of the fuse device shown in Fig. 1, partiallysectionalized to expose a portion of the fusible link member.

Fig. 3 is a perspective view of the fusible link member represented Fig.1, showing in de- 6 Claims. (Cl. 200-131) tail one embodiment of thelink spacing device of my invention.

Fig. 4 is a perspective view of the support spacing device of myinvention, as represented in Fig. 1.

Fig. 5 is a perspective view of a portion of a fusible link membershowing another embodiment of a link spacing device.

Fig. 6 is a side view of a portion of the removable inner assembly of atypical fuse having a combination of links, showing the link spacingdevice represented in Fig. 1 applied to a fuse having multiple links.

Referring now to Fig. l of the accompanying drawing, there isrepresented an electrical fuse of the renewable knife blade contact typecomprising principally, a tubular outer casing assembly i, a removableinner assembly 2, and an internally threaded cap member 3. Outer casingassembly I comprises a tubular casing 4 of insulating material such asfiber, a lower metal insert 5, and an upper metal insert 6, inserts 5and 6 being threadedly connected to casing 4 and securely anchoredthereto by rivets or the like. Removable inner assembly 2 comprisesprincipally a supporting bar I of insulating material such as fiber, apair of metal cleats 8 and 9 fixed to the ends of bar 1, a pair ofterminals such as knife blades i0 and l l securely attached to cleats 8and 9, a pair of lower guiding Washers l2 and i 3 having a spring washerl4 therebetween, a pair of upper guiding washers I5 and i6, and arenewable fusible link member I! attached to terminals [0 and II bysuitable holding devices, such as screws l8 and I9. Link I! comprises astrip 20 of fusible material having a plurality of mass members 2|attached to the opposite sides thereof in pairs. These pairs are locatedin longitudinal spaced relation along strip 20, forming in effect aseries of enlarged portions connected by restricted portions.

The parts of inner assembly 2 thus far enumerated are typical parts suchas may be found in a conventional electric fuse of the general typedescribed. In accordance with my invention, I provide, additionally, twospacing devices to accomplish objects as previously explained. Inparticular, I provide a spacer 22 attached directly to one of the massmembers 2| of fusible link 57. The preferred shape and application ofspacer 22 are shown most clearly in Fig. 3, wherein it is seen thatspacer 22 is a simple folded member, preferably metal, having a pair oflegs 23 and 24 disposed at a convenient angle, such as a right angle.Leg 23 is permanently attached, preferably by welding or soldering, to amass member 2| of link [7, and leg 24 is arranged to projecttransversely from link l1. Referring again to Fig. 1, it is seen thatprojecting leg 24 of spacer is arranged to engage supporting bar 1approximately at the longitudinal center thereof, substantiallypreventing buckling action of link I! in the direction of support 1,resulting from heating of link I! by a current flowing therein.

By the use of spacer 22, therefore, direct contact between link I! andsupport I, under operating conditions, is prevented. Direct transmissionof heat from link I! to support I is also thereby minimized. The amountof heat transmitted directly from link ll through spacer 22 to support Iis very small because of the fact that spacer 22 is attached to one ofthe mass members 2|, which is one of the cooler portions of the link [1,and because of, the fact thatthe spacer 22 itself is of a thin materialso that the projecting leg 24 is rapidly and efficiently cooled.However, heat from link ll tends to be transmitted to support 1 in otherways, as for example, by radiation and circulation of gases withintubular casing 4 A greater amount of heat is transmitted to the side ofsupport 1 adjacent to link ll by direct radiation fromthe link to causea greater heating and dryingaction forthis surface and a resultingwarping action to cause support I to bow away from link IT, or to theright, in contemplation of Fig. 1. This warping action, if permitted,causes the ends of the inner assembly, including cleats 3 and 9, to bespaced more closely together. This action tends to cause a closerspacing of link I l to support I, further aggravating the heating,drying and warping effect. A further undesirable result of the possiblewarping of support 1 is a twisting of the ends of inner assembly 2,including cleats 8 and 9, and knife blades [0 and H to cause knife bladeII] to tilt in a counter-clockwise, andblade II in a clockwise,direction, in contemplation of Fig. 1, which results in poor contactbetween the knife blades and the respective spring contact fuse holderreceptacles (not shown). Therefore, I provide a spacer 25 which isattached to and forms a part of supporting bar 1 to prevent theabove-described warping and deflection. The configuration of spacer 25is shown more clearly in Fig. 4, wherein it is seen that spacer 25 is asimple V-shaped folded member, preferably metal, having a pair of arms25 arranged to engage firmly the peripherypf supporting bar 1, arms 26being provided at one end with bendable fingers 21 arranged to engage apair of notches 28 located approximately at the longitudinal center ofbar 1. Extending from the other ends of arms 26 is a proi flting portion29 arranged to engage inner wall 30 of tubular casing 4. As may be seenin Fig. 1 any tendency of support 1 to Warp to the right, away from linkI7, is opposed by interference between projecting portion 29 and innerwall 30 of tubular casing 4. It will be seen from the above explanationthat spacer 25, by preventing warping deformation of support 1, assistsspacer 22 in preventing undesired proximity of link I! to support 7.

Reference to Fig. 6 indicates the manner in which link spacer 22 shownin Fig. 1 may be applied to a fuse having multiple links. Each of thelinks I! is provided with a spacer 22 attached thereto in the mannerpreviously described. It is obvious that if a fuse of the type shown inFig. 6 has only a single supporting bar, as i gen-- erally the case,only a single support spacer 25 need be provided.

In Fig. 5, I have shown another embodiment of a link spacer, comparablein function'to spacer 22, but differing therefrom in shape and method ofattachment to a link member such as link ll.

. In particular, spacer 3| shown in Fig. 5 takes the form of a springclip, preferably metal, having a center portion 32, a pair of arms 33projecting transversely from the ends of center portion 32, and a pairof fingers 34 projecting transversely and inwardly from the ends of arms33, forming in effect a C-shaped member.

The distance between fingers 34 is such that a clamping action existsbetween fusible strip 20 of link I! and fingers 34, when the latter areslidably positioned in slot 35 between a pair of mass members 2|. Suchclamping action maintains spacer 3| in the desired position with respectto link I! after attachment thereto.

A particular advantage of my invention is to be found in the provisionof separate spacing devices to perform the dual spacing functionspreviously described, namely spacing the fusible links away from thesupporting bar, and spacing the supporting bar away from the inner wallof the tubular casing. As will be understood by those skilled in theart, in the performance of a current interrupting operation by anelectrical fuse device, commonly described as blowing, an arc isgenerally formed between the disconnected portions of the fusible linkmember after melting action thereof has occurred due to excessivecurrent therein. A link spacing device, which of necessity must belocated adjacent to a link member, is subjected to the arcing actionoccurring when the fuse blows and may therefore be partially, if notentirely, destroyed. In a fuse of the renewable type, it is desirableupon renewing a fusible link after blowing of the fuse, that an integrallink spacing device be available to perform the link spacing function inconnection with the replaced link. In accordance with my invention, Iprovide a link spacer which is di rectly attached to the fusible linkmember, in effect forming a part thereof. With such an arrangement a newand therefore undamaged link spacer is automatically provided with eachreplacement link. In addition, when links are placed in multiple a linkspacing device is automatically provided with each link.

Furthermore, in accordance with my invention, I provide a supporting barspacer which is located on the opposite side of the supporting bar fromthe fusible link, thereby placing it in a position where it is leastlikely to :be damaged by an are between portions of the fusible link.Since the supporting bar is generally considered a permanent part of thefuse device not subject to replacement each time blowing of the fuseoccurs, it is obviously advantageous to provide a supporting bar spacerwhich is likewise a permanent part of the fuse device, and which neednot therefore be replaced whenever the fuse blows. Moreover, byproviding a spacer which maintains the bar in its proper position in thecasing, the link spacing device will always be effective to perform itsfunction of preventing undue bending and elongation of the link.

While I have shown certain preferred embodiments of my invention itshould be understood that my invention may well take other forms and Itherefore aim in the appended claims to cover all such modifications asare within the true 16 spirit and, scope of my invention,

What I claim as new and desire to secure by Letters Patent in the UnitedStates is:

1. An electric fuse of the renewable type comprising a tubular outercasing, an inner assembly including a supporting bar, a pair ofterminals attached to the ends thereof, a fusible link member connectedbetween said terminals, said inner assembly being removable from saidcasing for renewal of said link, means for preventing buckling of saidlink and closer spacing of said link to said supporting bar comprising afirst spacer integral with said supporting bar extending away from saidlink to the wall of said casing for preventing warping of saidsupporting bar and a second spacer integral with and renewable with saidlink extending toward said supporting bar to maintain a minimum spacingbetween said link and said bar.

2. An electric fuse of the renewable type comprising a tubular outercasing, an inner assembly including a supporting bar, a pair ofterminals attached to the ends thereof, a fusible link member of thetype having a plurality of alternately arranged enlarged and restrictedportions connecting said terminals, said inner assembly fbeing removablefrom said casing for renewal of said link, a spacer integral with andrenewable with said link comprising an L-shaped member having a long legfixedly attached to one of said enlarged portions of said link and ashort leg 7 extending toward said supporting bar to maintain a minimumspacing between said link and said bar.

3. An electric fuse of the renewable type comprising a tubular outercasing, an inner assembly including a supporting bar, a pair ofterminals attached to the ends thereof, a fusible link mem ber of thetype having a plurality of alternately arranged enlarged and restrictedportions connecting said terminals, said inner assembly being removablefrom said casing for renewal of said link, a spacer integral with andrenewable with said link comprising a metallic spring clip having acenter portion, a pair of arms projecting transversely from the ends ofsaid center portion, and a pair of fingers projecting transversely andinwardly from the ends of said arms, said fingers being arranged to beslidably attached to one of the enlarged portions of said link memberand to eifect clamped engagement therewith, said center portion beingarranged to engage said supporting bar and maintain said link in minimumspaced relation with said bar.

4. An electric fuse of the renewable type comprising a tubular outercasing, an inner assembly including a supporting bar having a pair ofnotches therein, a pair of terminals attached to the ends thereof, afusible link member connected between said terminals, said innerassembly being removable from said casing for renewal of said link, aspacer integral with said supporting bar for preventing warping of saidsupporting bar having a pair of arms and a pro- Jecting portion, saidarms being constructed and adapted to engage firmly the periphery ofsaid supporting bar said arms being provided at one end with bendablefingers arranged to engage firmly said pair of notches, said projectingportion extending from the other end of said arms, said projectingportion being arranged to engage said outer casing and maintain said barin minimum spaced relation with said casing.

5. An electric fuse of the renewable type comprising a tubular outercasing, an inner assembly including a supporting bar having a pair ofnotches therein, a pair of terminals attached to the ends thereof andeach including a knife blade contact, a fusible link member of the typehaving a plurality of alternately arranged enlarged and restrictedportions connecting said terminals, said inner assembly being removablefrom said casing for renewal of said link, means for preventing bucklingof said link and closer spacing of said link to said supporting barcomprising a first spacer and a second spacer, said first spacer beingintegral with said supporting bar and ex tending away from said link tothe wall of said casing for preventing warping of said supporting barand having a pair of arms and a projecting portion, said arms beingconstructed and adapted to engage firmly the periphery of saidsupporting bar, said arms being provided at one end with bendablefingers arranged to engage firmly said pair of notches, said projectingportion extending from the other ends of said arms, said projectingportion being arranged to engage said outer casing and maintain said barin minimum spaced relation with said casing; said second spacer beingintegral with an renewable with said link and comprising an L-shapedmember having a long leg fixedly attached to one of said enlargedportions of said link and a short leg extending toward said supportingbar to maintain a minimum spacing between said link and said bar.

6. A fusible link member for use in an electric fuse of the renewabletype including an insulating supporting bar, said link having aplurality of alternately arranged enlarged and restricted portions, aspacer integral with and renewable with said link comprising an L-shapedmember having a long leg fixedly attached to one of said enlargedportions of said link and a short leg for extending toward saidsupporting bar to maintain a minimum spacing between said link and saidbar.

FRED G. VON HOORN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 755,796 Sargent Mar. 29, 19041,363,642 Candee et al. Dec. 28, 1920 1,881,351 Bussmann Oct. 4, 19321,950,489 Glowacki Mar. 13, 1934

